gnu/packages/patches/guile-fibers-epoll-instance-is-dead.patch

   1 From 5db4077e9f5166033637d2af9532ec6144b85646 Mon Sep 17 00:00:00 2001
   2 From: Maxime Devos <maximedevos@telenet.be>
   3 Date: Thu, 30 Jun 2022 14:21:47 +0000
   4 Subject: [PATCH 1/2] Fix behaviour of 'epoll-wake!' after 'run-fibers'.
   5
   6 This avoids the "epoll instance is dead" error noticed in
   7 GNUnet-Scheme's test suite, as reported at
   8 <https://github.com/wingo/fibers/issues/61>.
   9 A test is added in the next commit.
  10
  11 This patch has been applied upstream, but there hasn't been
  12 a new release yet at time of writing.
  13
  14 * fibers/epoll.scm (epoll-wake!)[dead]: Instead of throwing an error,
  15 just return #t.
  16 ---
  17  fibers/epoll.scm | 8 +++++++-
  18  1 file changed, 7 insertions(+), 1 deletion(-)
  19
  20 diff --git a/fibers/epoll.scm b/fibers/epoll.scm
  21 index d26db4d..eb63242 100644
  22 --- a/fibers/epoll.scm
  23 +++ b/fibers/epoll.scm
  24 @@ -1,6 +1,7 @@
  25  ;; epoll
  26
  27  ;;;; Copyright (C) 2016 Andy Wingo <wingo@pobox.com>
  28 +;;;; Copyright (C) 2022 Maxime Devos <maximedevos@telenet.be>
  29  ;;;;
  30  ;;;; This library is free software; you can redistribute it and/or
  31  ;;;; modify it under the terms of the GNU Lesser General Public
  32 @@ -135,7 +136,12 @@ epoll wait (if appropriate)."
  33      ('waiting
  34       (primitive-epoll-wake (fileno (epoll-wake-write-pipe epoll))))
  35      ('not-waiting #t)
  36 -    ('dead (error "epoll instance is dead"))))
  37 +    ;; This can happen if a fiber was waiting on a condition and
  38 +    ;; run-fibers completes before the fiber completes and afterwards
  39 +    ;; the condition is signalled.  In that case, we don't have to
  40 +    ;; resurrect the fiber or something, we can just do nothing.
  41 +    ;; (Bug report: https://github.com/wingo/fibers/issues/61)
  42 +    ('dead #t)))
  43
  44  (define (epoll-default-folder fd events seed)
  45    (acons fd events seed))
  46
  47 From c01d3853eb56ea4adacc31f51f6e917f8c0abe1c Mon Sep 17 00:00:00 2001
  48 From: Maxime Devos <maximedevos@telenet.be>
  49 Date: Thu, 30 Jun 2022 14:18:36 +0000
  50 Subject: [PATCH 2/2] Test for issue #61.
  51
  52 * tests/conditions.scm: Add a test.
  53 ---
  54  tests/conditions.scm | 20 ++++++++++++++++++++
  55  1 file changed, 20 insertions(+)
  56
  57 diff --git a/tests/conditions.scm b/tests/conditions.scm
  58 index 505c42a..179605a 100644
  59 --- a/tests/conditions.scm
  60 +++ b/tests/conditions.scm
  61 @@ -1,6 +1,7 @@
  62  ;; Fibers: cooperative, event-driven user-space threads.
  63
  64  ;;;; Copyright (C) 2016 Free Software Foundation, Inc.
  65 +;;;; Copyright (C) 2022 Maxime Devos <maximedevos@telenet.be>
  66  ;;;;
  67  ;;;; This library is free software; you can redistribute it and/or
  68  ;;;; modify it under the terms of the GNU Lesser General Public
  69 @@ -21,6 +22,7 @@
  70    #:use-module (fibers)
  71    #:use-module (fibers conditions)
  72    #:use-module (fibers operations)
  73 +  #:use-module (fibers scheduler)
  74    #:use-module (fibers timers))
  75
  76  (define failed? #f)
  77 @@ -78,4 +80,22 @@
  78                               (wait cv)
  79                               #t))
  80
  81 +;; Make a condition, wait for it inside a fiber, let the fiber abruptly
  82 +;; terminate and signal the condition afterwards.  This tests for the bug
  83 +;; noticed at <https://github.com/wingo/fibers/issues/61>.
  84 +(assert-equal #t
  85 +             (let ((cv (make-condition)))
  86 +               (run-fibers
  87 +                (lambda ()
  88 +                  (spawn-fiber (lambda () (wait cv)))
  89 +                  (yield-current-task)) ; let the other fiber wait forever
  90 +                ;; This test relies on not draining -- this is the default,
  91 +                ;; but let's make this explicit.
  92 +                #:drain? #false ;
  93 +                ;; For simplicity, disable concurrency and preemption.
  94 +                ;; That way, we can use 'yield-current-task' instead of an
  95 +                ;; arbitrary sleep time.
  96 +                #:hz 0 #:parallelism 1)
  97 +               (signal-condition! cv)))
  98 +
  99  (exit (if failed? 1 0))